Emission after-treatment devices are used to collect particulate matter from the exhaust gas of internal combustion engines. In particular, emission treatment devices may include particulate filters, oxidation catalysts, and nitrous oxide (NOx) catalysts. A problem exists with particulate filters in that the particulates, which are largely made up of carbon particles, tend to plug the filters, restricting the flow of an exhaust gas. In order to periodically regenerate or purge the filter of particulates, it is known to take measures which result in an increase of the exhaust gas temperature above a predetermined level (e.g. above 600° C.) in order to incinerate the carbon particles accumulated in the filter.
One method used to increase the exhaust gas temperature may involve controlling a throttle valve in the intake manifold of the engine. In particular, by throttling/closing the throttle valve, the exhaust gas temperature may be increased for all cylinders, to the detriment of fuel economy. Gas particulate filters that are targeted by such regeneration methods may be placed upstream of a turbine and downstream of an exhaust manifold. One example approach is shown by Winsor et al. in U.S. Pat. US20090077954. The non-catalyzed particulate filter described therein receives exhaust gas with temperatures high enough, after a combustion event with an excess of air, to regenerate the filter.
However, the inventors herein have recognized potential issues with such systems. As one example, these systems place the particulate filter outside the exhaust manifold and as a result utilize increased engine adjustments to raise exhaust gas temperatures and cause an overall reduction in fuel economy. As a second example, use of a single, large particulate filter provides an engine system with few diagnostic capabilities. If an individual cylinder injector spray is degraded, a system with a single, large particulate filter cannot diagnose the degradation because the exhaust of one cylinder has a minimal effect on the particulate filter receiving exhaust from a plurality of cylinders.
In one example, the issues described above may be addressed by flowing exhaust from a first cylinder through a first particulate filter in a first runner, flowing exhaust from a second cylinder through a second particulate filter in a second runner, and adjusting engine operation in response to particulate filter degradation, the particulate filter degradation distinguishing between degradation of the first and second particulate filter based on exhaust pressure pulsation timing relative to combustion events. An engine controller may detect a high particulate matter load in a particulate filter or a leaking/missing particulate filter in the exhaust runner of an individual engine cylinder based on a comparison of a measured exhaust pressure amplitude against a threshold. In this way, each individual particulate filter may be independently evaluated for particulate matter load and fouled particulate filters may be independently regenerated by adjusting operation of only the engine cylinder corresponding to that fouled particulate filter. The inventors have also recognized that independent particulate filter fouling may indicate a fouled or otherwise degraded fuel injector. For example, an individual particulate filter with a higher than expected or average particulate matter load may indicate that the fuel injector for the associated cylinder is exhibiting a deviating spray pattern (e.g., due to matter build-up on the injector nozzle) that causes incomplete combustion or otherwise results in high particulate matter output from the cylinder. By increasing the cylinder temperature to regenerate the particulate filter as described above, the matter build-up on the fuel injector may also be reduced to reduce overall particulate matter output from the cylinder. Furthermore, the inventors have realized that positioning the individual particulate filters within the exhaust runners enables particulate filtering in such filters to be increased relative to filtering with particulate filters positioned further downstream due to higher heat being present the exhaust runner than other downstream areas in which particulate filters may be located in other vehicle configurations.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.